The present invention is directed to a method of preparing imidazolium surfactant. The present invention is also directed to a nano-composite comprising the imidazolium surfactant and a clay, and a composition comprising the nano-composite and a polymer. The composition is useful in preparing rubber products with well-balanced gas impermeability, cure properties, and mechanical properties etc.
In manufacturing a satisfactory rubber product, one needs to consider a wide range of factors and various balances between them, such as gas permeability, curing properties such as curing time and curing capability, traction characteristics on dry or wet surface, rolling resistance, tread-wear resistance, ring tensile, vulcanization plateau, Shore A hardness, rubber damping properties, elongation, strain, specific gravity, reliability, manufacturability, and cost effectiveness, among others. For example, gas impermeability is important for many products such as butyl rubber, because unsaturated bonds in butyl rubber can be attacked by atmospheric ozone. These attacks may, over time, lead to oxidative degradation, which may subsequently lead to chain cleavage. As such, there exists a continuous interest in lowering gas permeability of polymers.
Since the discovery of exfoliated nylon/clay nano-composites by Usuki et al. (J. Mater. Res. 1993, 8, 1174), people have made extensive efforts to lower gas permeability by using well-exfoliated layered materials. A common morphology for miscible polymer-layered material dispersions is known as intercalation and exfoliation, which improves polymeric mechanical, gas barrier/permeability, thermal, and heat distortion temperature properties. However, for polymers, particularly nonpolar polymers, well-exfoliated polymer-layered material nano-composites are notoriously difficult to obtain. For example, Wang et. al in the Journal of Applied Polymer Science, Vol. 78, 1879-1883 (2000) describe a process of making clay-rubber mixtures by mixing a styrene-vinylpyridine-butadiene latex with a hydrophilic unmodified clay. The expansion of the clay gallery was reported to only increase from 1.24 to 1.46 nm. This limited extent of intercalation is not expected to provide substantial property enhancement.
Although organic ammonium salts have shown improved clay exfoliation, they typically have a low decomposition temperature. Accordingly, these materials cannot be extruded at high temperature as may be required with a resin such as nylon, PP, PET, etc. Furthermore, organo-clays treated by the ammonium salts may damage or retard the cure process of the rubbery material, especially when free radical sulfur, or ZnO cure are employed.
Advantageously, the present invention provides a method of preparing an imidazolium surfactant that may have a high decomposition temperature. The imidazolium surfactant may be used to prepare nano-composites such as organo-clays and products including the nano-composites.